This invention relates to a printing press, and particularly to apparatus for adjusting the printing press for accommodating different sizes of paper webs, or the like webs, which are being imprinted. The invention is useful for printing presses which are equipped with printing plate cylinders that are adapted to replaceably support various printing plates. The printing plates are of different sizes for printing different size paper sheets.
Such a printing press is also provided with at least one folder adapted for handling different size sheets being printed and folded. Such printing presses comprise at least one paper sheet cutting means, a folding cylinder, which usually carries a folding knife blade thereon, and a gripper cylinder which is installed coaxially with the folding knife cylinder and which is adjustable in its rotative phase position with respect to the folding knife cylinder.
Printing presses, and particularly rotogravure presses, use printing plate cylinders which replaceably carry different size printing plates. The sizes of these plates and the sizes of the paper which they print are variable during different printing runs. As a result, the folding apparatus associated with these presses must be internally adapted to different sheet sizes. Additionally, the printing units must also be adapted to the folding apparatus, or vice versa, because although the length of the run of the paper web, between the section of the printing press at which the web is printed and the subsequent folding apparatus remains constant, the number of pictures and/or the size of the imprint on the web changes and adjustments for this are required.
In order to minimize the down time between two successive printing runs, presetting programs have been established for such printing presses. At the start of a new printing run, the cutting and inking registers are already preset so precisely that they lie within the target range of an electronic scanner. The scanner corrects the preset registers rapidly for particular size sheets, with minimum loss of time and minimum misprints. Whether it is operated manually or by automatic devices, the presetting program is complicated if a large number of settings prove necessary. The presetting program is correspondingly simplified if the number of settings can be limited to only a few. The invention is based upon the realization that there is only a minimum number of required settings if all settings rely upon an invariable reference point. It is preferred that the point at which the web is cut into sheets be used as the reference point. A different fixed reference point may be selected, such as the first transverse fold, as has previously been the case. In such a case, for example, when a printing press is alternated between four and six engravings, for the same size paper, two different cylinder circumferences are possible. This complicates the presetting program.
Programmed presetting of printing units with respect to each other and of all of the printing units with respect to the folding apparatus is already frequently employed. However, simultaneous presetting of all elements of the folding apparatus has not previously been known.